#include <stdio.h>
int main()
{
    int max();
    extern int A, B, C;
    printf("Please enter three integer numbers:");
    scanf("%d %d %d", &A, &B, &C);
    printf("max is %d\n", max());
    return 0;
}

int A, B, C;

int max()
{
    int m;
    m = A > B ? A : B;
    if (C > m)
        m = C;
    return m;
}